Roofing stones in building construction: Which rock is most commonly used for roofing slabs because it naturally splits into thin, durable sheets?

Introduction / Context:
Traditional roofing in many regions uses natural stone slabs. The suitability of a rock for roofing depends on its ability to split into thin, strong, weather-resistant sheets with a pleasant appearance and adequate durability.

Given Data / Assumptions:

• Roofing requires thin, flat, strong panels.
• The stone should have good cleavage for splitting and good weather resistance.

Concept / Approach:
Slate, a metamorphic rock derived from shale, exhibits slaty cleavage, allowing it to be split into thin, uniform slabs. It is durable, resists water penetration, and provides long service life. Granite and basalt are strong but do not split as cleanly into thin roofing slabs; pumice is too porous and weak for structural roofing sheets.

Step-by-Step Solution:

Verification / Alternative check:
Historic and modern slate roofs worldwide (Wales, Spain, India, USA) confirm slate’s ubiquitous use where available, due to its cleavage and weathering performance.

Why Other Options Are Wrong:

• Granite/Basalt: very strong but unsuitable for thin splitting; machining to thin slabs is expensive and impractical for roofing.
• Pumice: too soft and porous; not a structural roofing sheet material.

Common Pitfalls:

• Confusing decorative stone facings with roofing slabs; cladding has different thickness and attachment.

Final Answer:
slate